In the prior art, systems are known which make it possible to transfer liquid natural gas, at sea, between two ships. By way of example, document WO0134460 discloses a system which makes it possible to transfer liquid natural gas between a liquid natural gas production ship and a liquid natural gas transport ship. The transfer system comprises three parallel flexible ducts, two of which make it possible to transfer the liquid natural gas from the production ship to the transport ship, whereas the third duct makes it possible to transfer gas from the transport ship to the production ship in order to balance the pressures in the gaseous headspaces of the tanks of the two ships, and thus to prevent the pressure inside the tank of the production ship from dropping. The three flexible ducts are suspended on a mast which is fitted such as to be mobile on the deck of the production ship, and have a free end equipped with an element for connection to a collector, commonly known as a manifold, of the liquid natural gas transport ship.
A transfer system of this type does not give entire satisfaction. In fact, when the sea is rough, the relative movements between the two ships make the movements of the flexible ducts random, and makes them particularly complicated to handle. The maneuvering difficulties thus make the operations of connection of the flexible ducts to the manifold of the transport ship lengthy to carry out and insecure.